Secondary-stage throttle control for a multi-stage carburetor



Feb. 11, 1958 R. J. SMITH 2,823,020 SECONDARY-STAGE THROTTLE comm. FOR A MULTI-STAGE CARBURETOR Filed April 27, 1956 2 Sheets-Sheet l m w m m ROBERT J. SMlTH 0m/%% AITORNEY Feb. 11, '1958 v R; .1. SMITH 2,823,020

SECONDARY-STAGE THROTTLE CONTROL FOR A Filed April 27, 1956 MULTI-STAGE CARBURETOR 2 Sheets-Sheet 2 ATTORNEY United States Patent SECONDARY-STAGE THROTTLE CONTROL FOR A MULTI-STAGE CARBURET OR Robert J. Smith, Overland, Mo., assignor, by mesne assignments, to ACF Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application April 27, 1956, Serial No. 581,133

13 Claims. (Cl. 261-23) This invention relates to carburetors for internal combustion engines, and more particularly to two-stage carburetors of the type having one or more mechanically operated primary throttles and one or more secondary throttles unbalanced to close by suction and mechanically biased to open as, for example, by a spring.

To match the output of a two-stage carburetor of the class described to the requirements of the engine supplied with fuel thereby, so as to obtain smooth idling and good all-around performance of the engine, it is important that the secondary throttle or throttles of the carburetor be maintained closed during idling and throughout part of the range of opening movement of the primary throttle or throttles. The principal object of this invention is to insure that the secondary throttle or throttles are maintained closed during idling and throughout part of the range of opening movement of the primary throttle or throttles, and to obtain release of the secondary throttle or throttles to permit them to open under the stated mechanical bias upon a predetermined opening of the primary throttle or throttles. This object is obtained, according to the present invention, by providing a latch for maintaining the secondary throttle or throttles closed against the opening bias, and suction-responsive means for operating the latch, the latter being adapted to release the latch in response to suction developed upon partopening of the primary throttle or throttles. A further feature of the invention is the provision of means interconnecting the primary throttle or throttles and the secondary throttle or throttles adapted to overcome the opening bias on the secondary throttle or throttles so that they may return to closed position during the return of the primary throttle or throttles to closed position, and which permits the opening of the secondary throttle or throttles under the stated mechanical bias upon release of the latch. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly'compn'ses the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which one of various 9 possible embodiments of the invention is illustrated,

Fig. l is a view in elevationof one end of a four barrel carburetor embodying the invention, with parts broken away and shown in section, and showing the primary and secondary throttles in closed position andthe latch for thesecondaryithrottles in looking position;

Fig. 2 is a fragment of Fig. 1 showing the latch released, and showing the primary throttles partly opened but the secondary throttles still closed;

Fig. 3 is a view similar to Fig. 2 showing the primary and secondary throttles wide open;

Fig. 4 is a view in elevation of the other end of the carburetor from that shown in Fig. 1, showing the primary and secondary throttles in closed position; and,

Fig. 5 is a vertical transverse'sectionshowingone primary mixture conduit (barrel) and the associated secondary mixture conduit (barrel) of the carburetor.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the drawings, the invention is illustrated in its application to a multi-barrel, multi-stage carburetor 1 of the type commonly referred to as a four-barrel carburetor. Only so much of the construction of the carburetor as is essential to an understanding of this invention will be described herein. Reference may be made to Carlson et al., U. 8. Patent 2,715,522, dated August 16, 1955, for example, for such further details as may be desired.

In general, the carburetor 1 comprises a fuel bowl section 3 having a flange 5 by which it may be attached to the intake manifold of the engine on which the carburetor is used. Mounted on the fuel bowl 3 is the usual air horn section 7. The fuel bowl section 3 is formed to provide two primary mixture conduits and two secondary mixture conduits. One primary mixture conduit, designated 9, and one secondary mixture conduit, designated 11, appear in Fig. 5. The air horn section 7 is provided with a partition 13 dividing it to form a primary mixture conduit inlet 15 and a secondary mixture conduit inlet 17.

A choke valve 19 is provided inthe primary inlet 15 for controlling the admission of air through the air horn section 7 to the two primary mixture conduits 9. The

choke valve is fixed on a choke shaft 21 which extends across the air horn section 7 from one end to the other above the primary mixture conduits (one of which is shown at 9 in Fig. 5). Each primary mixture conduit 9 has a main venturi 23 and a primary venturi 25. As to each of the primary mixture conduits 9, a main fuel nozzle 27 opens into its primary venturi 25. It will be understood that the nozzles 27 are supplied with fuel from the fuel bowl section 3 in a manner such as that shown, for example, in U. S. Patent 2,715,522.

A primary throttle 29 is provided in each primary mixture conduit 9 below the main venturi 23. The primary throttles for both conduits 9 of the four-barrel carburetor are fixed on a throttle shaft 31 which extends across both these conduits. Adjacent one edge of each throttle 29 are the usual idle ports 33 and 35 which are supplied with fuel via a passage indicated at 37. The port 35 is controlled by an adjustable needle valve 39 in known manner.

Each secondary mixture conduit 11 has a main venturi 41 and a primary venturi 43. A fuel nozzle 45 opens into the primary venturi 43. This is supplied with fuel from the fuel bowl in a manner such as that shown, for example, in U. S. Patent 2,715,522. A secondary throttle 47 is provided in each secondary mixture conduit 11 below the main venturi 41. The secondary throttles for both conduits 11 of the four-barrel carburetor are fixed on a shaft 49 which extends across both these conduits. The secondary throttles 47 are unbalanced to close by suction in the secondary mixture conduits and are biased to open by a torsion spring 50 (see Figs. l-3).

A choke mechanism housing is indicated at 51 (see Fig. 1). This contains a suction and temperature-responsive mechanism of the character shown in the Coffey U. S.'Patent 2,325,372. This mechanism includes a control arm indicated at 53 connected by means of a link 55 to an arm 57 fixed on the end of the choke shaft 21 shown in Fig. 1 projecting out of air horn section 7. Fixed on the other end of the choke shaft 21 (at the other end of the air horn section 7) is an arm 59 (see Fig. 4). Arm 59 is connected by means of a link 61 to a fast idle cam lever 63 pivoted on the outside of fuel bowl section 3 at'65. A lever 67 is fixed on the end of the primary' throttle shaft 31 shown' in Fig. 4. At the end of the lever 67 is an inturnedlug 69 adapted'to engage the fast idle cam lever 63 when the primary throttle is fully opened, so as partially to open the choke valve 19 for unloading purposes. The primary throttle shaft 31 .also carries an actuating lever 71 provided with a hole 73-for connection of an actuating rod (not shown). A lug 75 on the lever 71 has an idle set screw 77 threaded therein for adjusting the closed position of the primary throttles 29. Lever 71-is connected by a link 79 to one end of a pivoted lever 81 adapted to operate the plunger 83' of an accelerating pump (not shown).

A lever 85 is rotatable on the end of the secondary throttle shaft 49 shown in Figs. l-3. Lever 85, at one end, has spaced opposed shoulders 87 and 88. An inturned lug 89 on an arm 91-tixed to the secondary throttle shaft 49 extends between these shoulders. Lug 89 is narrower than the distance between the shoulders. A link 93 interconnects the other end of the lever and one end ofa lever 95 rotatable on the end of the primary throttle shaft 31- shown in Figs. l3. The spring 50 has one end attached to a pin 97 on fuel bowl section 3 of the carburetor and its other end hooked in a notch in lever 85-as indicated at 99. It biases the lever 85 in clockwise direction as viewed in Figs. l3, andthe lever 85 is adapted to act through engagement of shoulder 87 with lug 89 on arm 91 to bias the secondary throttle shaft 49 in opening direction (clockwise as viewed in Figs. l3). Lever 95, at its other end, has a shoulder 101 engageable by an inturned lug 103 on an arm 195 fixed to the primary throttle shaft 31. The lug 103 engages shoulder 1111 upon rotation of the primary throttles 29 and the primary throttle shaft 31 in closing direction (clockwise as viewed in Fig. l) to rotate the lever 95 clockwise as viewed in Fig. 1.

When the primary throttles 29 are closed (see Figs. 1, 4 and 5 the lug 1113, lever 95, link 93 and lever 85 occupy the retracted position shown in Fig. 1. In this retracted position of the lever 85, its shoulder 87 is engageable with a latch 1.67 operated by suction-responsive means indicated at 1119. This.suction-responsive.means 109 is constituted by a diaphragm-type suctionmotor at the end of the carburetor shown in Fig. 1 comprising cups 111 and 113 secured together at their rims and a flexible diaphragm 115 having its marginclamped between the rims. The cups form chambers 117 and 119 on opposite sides of the diaphragm. The latch 1tl7 is constituted by a rod fixed in the center ofv the. diaphragm and,

slidable in an axial opening 121;in the. cup 113. A spring 123 housed in the cup 111 biases the diaphragm115 and the rod 197 toward the locking position shown in Fig. l in which the outer end of the rod projects out of the cup 113, for engagement by the shoulder 87 on lever 85 to lock the lever 35 in retracted position against the bias of the spring 50.

The fuel bowl section 3 of the carburetor is formed with a passage 125 which opens at one end to the chainber 117 of the suction motor 1119, and which has branch connections such as indicated at 127 to the main ve nturis 23 of the primary mixture conduits 9. Each branch connection 127 has a restricted bleed 129. The cup113 has a passage 131 which intersects the axial opening 121. A plug for this passage is indicated at 133. The latch rod 107 is formed with an annular groove 135.to act as a valve for closing the passage 131Iwhen. in the locking position shown in Fig. l and for opening the passage 131 when moved toward the retractedposition shown in Figs. 2 and 3. The fuel bowl section 3 is formed with a passage 137 which opens at one end to the passage 131 posterior to the rod 107 and which communicates with the secondary mixture conduits 11. posterior to the secondary throttles 47. A restriction isfproe vided in passage 131 as indicated at 139; An atmospheric bleed 141 is provided in cup.113.'

Operation is as follows:

The chokev-alve 19, the primary throttles 29. and the.

secondary throttles 47 are shown closed in Figs. 1, 4 and 5. The lever 85, which with spring 50 constitutes means for biasing the secondary throttles 49 to open, is locked out of operation (with spring 5r? loaded) by the engagement of shoulder 37 with the latch 1117. With the second ary throttles 47 closed and the shoulder 87 in latching engagement with latch 87, there is some clearance (see Fig. 1) between the lug 89 on arm 91 and the shoulder 87. This insures tightclosing of the secondary throttles 47.

Upon opening the primary throttles 29, the lever 95, link 93 and lever initially remain in the Fig. l position, the arm 105 rotating counterclockwise with the primary throttle shaft 31 as viewed in Fig. 1 to a position such as shown in Fig. 2. Assuming that the engine supplied with fuel by the carburetor is in operation, suction is developed in the primary mixture conduits 9. As the primary throttles are opened, this suction, which is communicated to chamber 117 via passages 127' and- 125, ultimately becomes sufficient to effect flexure of the diaphragm 115. to theleft as.viewed in Fig. 1 against the biasiof. spring 123 to withdraw the latch 107 from the shoulder 87 on. lever 85 (see. Fig. 2). Lever 85 is thereby released and spring 5% acts through the lever SSand lug,89.on arm91 to bias the secondary throttles in opening direction (clockwise as viewed in Fig. l). Upori clockwise movement of the lever 85 from the Fig. 2 position, lever is rotated counterclockwise by the link 93 The clockwise rotation of lever 85 is limited by engagementof the shoulder 101 on lever 95 with the lug 103 on arm on the primary throttle shaft 31. Thus, upon retraction of the latch 107, the secondary throttles are biasedv to open by the spring 50, with a limit upon their opening movement determined by the degree of opening of the primary throttles.

Fig. 3 shows the parts in the position assumed when the primary and secondary throttles are wide open. Upon return of the primary throttles toward closed position (clockwise rotation of the primary throttles 29, shaft 31 and arm 105 from the Fig. 3 position), the lug 1113 en gages shoulder 101 on lever 95 and rotates this lever clockwise. Lever 95 acts through link 93 to rotate lever 85 counterclockwise. The shoulder 83 on lever 85 thereuponengages the lug 89 on arm 91 and rotates the arm 91 and the secondary throttle shaft 49 counterclockwise to return the secondary throttles 47 toward closed position. Thisperrnits the secondary throttles 47 to return toward closed position under the section of suction in the secondary mixture conduits 11.

When the latch 107 is retracted, with resultant opening of passage 131, suction developed in the secondary mixture" conduits is communicated. to chamber 119 via passages 137'and 131'. This lowers the pressure in chamher 119 aindreduces the pressure diiferential between chambers 119 and 117. Return of the primary throttles 29 toward closed position reduces the suction (increases the pressure) in chamber 117. When the suction in chamber 117 is-sufiiciently reduced, thelatch is moved to its Fig. 1 locking position. Accordingly, when the lever 85 hasreturned to theretracted position in which it is shown in Figs. 1' and 2, it is re-latched.

From the above, it will be apparentthat the means for biasing t h e secondary throttles 4 7 to open (spring 50 and. lever '85). is locked out of operation so that the secondarythrottlesv are maintained closed when the primary throttles/are closed andthroughout part of the range of opening rnovement of the primary throttles due to the fact that suction in the primary mixture conduits 9 and the chamber 117 is insufficient to retract the latch 107 until the primary throttles are opened beyond a certain amount. As soon as the latch is retracted, the secondary throttles are released to be spring-biased open in opposi tion to. suction in the secondary mixture conduits. The arm,105, lever 95, link 93, lever 85 and arm 91 constitute lost-motionmeans interconnecting the primary and secondary... throttles. for'eflfecting return of the secondary throttles to closed position upon return of the primary throttles-toward closed position, the lost motion allowed by this means permitting the primary throttles to be partly opened without opening the secondary throttles.

While the invention is herein illustrated as it pertains to a four-barrel carburetor, it will be understood that its principles are equally applicable to a two-barrel carburetor (one primary barrel and one secondary barrel). It is contemplated that spring 123 may be used alone for returning the latch 107 to locking position, or that the spring 123 may be omitted and that the latch be returned to locking position by suction in chamber 119.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, means for maintaining the secondary throttle in closed position when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, means biasing the latch to locking position, and means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position against the bias and responsive to suction in the secondary mixture conduit for returning the latch to locking position.

2. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, means for maintaining the secondary throttle in closed position when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, and means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position andresponsive to suction in the secondary mixture conduit for returning the latch to locking position.

3. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, the secondary throttle being unbalanced to close by suction, means biasing the secondary throttle to open, and means for locking the 'biasing means out of operation when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, and means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position and responsive to suction in the secondary mixture conduit for returning the latch to locking position.

4. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, the secondary throttle being unbalanced to close by suction, means biasing the secondary throttle to open, and means for locking the biasing means out of operation when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, means biasing the latch to locking position, and

means responsive-to a predetermined suction in the primary mixture conduit for moving the latch to retracted position against its bias and responsive to suction in the secondary mixture conduit for returning the latch to locking position.

5. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, the secondary throttle being unbalanced to close by suction, means biasing the secondary throttle to open, and means for locking the biasing means out of operation when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, and means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position and responsive to suction in the sec-- ondary mixture conduit for returning the latch to locking position.

6. In a carburetor having a primary throttle and a secondary throttle, means for'maintaining the secondary throttle in closed position comprising a latch movable between a locking position and a retracted position, suction-responsive means for moving the latch to retracted position to allow the secondary throttle to open and responsive to suction in the secondary mixture conduit for returning the latch to locking position, and means interconnecting the primary and secondary throttles for effecting return of the secondary throttle to closed position upon return of the primary throttle toward closed position.

7. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, means for maintaining the secondary throttle in closed position when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position .and a retracted position, means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position to all-ow the secondary throttle to open and responsive to suction in the secondary mixture conduit for returning the latch to locking position, and lost-motion means interconnecting the primary and secondary throttles for eifecting return of the secondary throttleto close position upon return of the primary throttle toward closed position.

8. In a carburetor having a primary throttle and a secondary throttle, the secondary throttle being unbalanced to close by suction, means biasing the secondary throttle to open, and means for locking the biasing means out of operation when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position, suction-responsive means for moving the latch to retracted position to allow the biasing means to act to open the secondary throttle and responsive to suction in the secondary mixture conduit for returning the latch to locking position, and means interconnecting the primary and secondary throttles for efiecting return of the secondary throttle to closed position upon return of the primary throttle toward closed position.

9. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary mixture conduit, the secondary throttle being unbalanced to close by suction, means biasing the secondary throttle to open, and means for locking the biasing means out of operation when the primary throttle is closed and throughout part of the range of opening movement of the primary throttle comprising a latch movable between a locking position and a retracted position,

means responsive to a predetermined suction in the pri mary mixture conduit for moving the latchqtoretracted position to allow the secondary throttle to open and responsive to suction in the secondary mixture conduit for returning the latch to locking position, andlost-rnotion means interconnecting the primary and secondary throttles for effecting return of the secondary throttle to closed position upon return of the primary throttle toward closed position.

10. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle on a primary throttle shaft in the primary mixture conduit, a secondary throttle on a secondary throttle shaft in the secondary'mixture conduit, the secondary throttle being unbalanced to close by suction, a member fixed on the secondary throttle shaft, a lever rotatable on the secondary throttle shaft and engageable with said member on rotation in one direction to open the secondary throttle, a spring ,biasing the leverto rotate in the direction to open the secondary throttle, and means for locking the lever in a retracted position allowing for closure by suction of the secondary throttle comprising a latch, and suction-responsive means for. operating the latch,

said latch comprising a valve portion controlling a sue-V tion passage from said secondary conduit to said suction responsive means.

11. In a carburetor having a primary mixture conduit, a secondary mixture conduit, a primary throttle on a primary throttle shaft in the primary mixture conduit, a secondary throttle on a secondary throttle shaft in the secondary mixture conduit, the secondary throttle being unbalanced to close by suction, a member fixed on the secondary throttle shaft, a lever rotatable on the secondary throttle shaft and engageable with said member on rotation in one direction to open the secondary throttle, a spring biasing the lever to rotate in the direction to open the secondary throttle, and means for locking the lever in a retracted position allowing for closure of the secondary throttle by suction comprising a latch movable between a locking position wherein it is engageable by the lever when the latter is in retracted position and a retracted position clear of the lever, and means responsive to a predetermined suction in the primary mixture conduit for moving the latch to retracted position and responsive to suction in the secondary mixture conduit for returning the latch to locking position.

12; In a carburetor having a primary mixture conduit, asecondary mixture conduit, a primary throttle on a primary throttle shaftginthe primaryrmixture conduit; a secondary throttle, one a secondary. throttleshaft'm the secondary mixture conduit, the secondarysthrottle. being lever in a retracted position allowing for closure of the secondary throttle by suction comprising a latch movable between a locking-position wherein it is engageable-by the first lever when the latter is in retracted position and a retracted position clear; of the firstlever, and means responsive toa predetermined suction in the primary mixture conduit for moving the latch to retractedgposition.

13. In a carburetor having a primary mixture conduit and a secondary mixture conduit, a primary throttle in the primary mixture conduit, and a secondary throttle in the secondary, mixture conduit, a suction motor on the carburetor comprising apressure-responsive member and means forming first and second chambers OHHOP' posite sides of said pressure-responsive member, said carburetor having a first passage providing forcomrnunication between the first chamber and the primary mixture conduit and asecond passage providing for communication between the second chamber and the secondary mixture conduit, and a combination secondary throttle latch and valve member for the second passage fixed to the, pressure-responsive member andmovable therewith between a locking position in which it blocks the second passage anda retracted position in which it opens the second passage.

References Cited in the file of this patent, UNITED STATES PATENTS 2,193,533 Kishline et al. Mar. 12, 1940 2,420,925 Wirth H May 20, 1947 2,609,806 Winkler Sept-. 9, 1952 2,752,133 Egerer June/26, 1956' 

